RGBLink VSP 729 - Manual (Page 54)

4.Menu Orientation
MENU
VSP 729 User Manual 54
DE Width；
DE Height；
When signal work on the display,the side of display show black,Use this
setting to make the full-screen.Select Program Press NEXT to select the
output interface HDMI/DVI.Normal interface is DVI,Select HDMI when need
to HDMI.The same way can set Preview.